The present invention relates to a sectional roll-up door. More particularly this invention concerns such a door used on a walk-in refrigerator or generally between a very cold space and a much warmer space.
A standard roll-up sectional door has a plurality of horizontally elongated rigid panels having inside and outside faces and upper and lower edges. Hinges on one of the faces between the panels define normally horizontal pivot axes and the ends of the panels are provided with rollers riding in L-shaped guides that each have one leg extending vertically adjacent an opening to be closed by the door and another leg extending horizontally to one side of and above the opening. Thus the door can be moved from a vertical closed position with the panels all lying in an upright plane and their edges engaging each other so as to block the opening to a horizontal open position above the door clear of the opening. As the door moves from the vertical closed position to the horizontal open position the panels pivot relative to each other as they pass from the vertical to the horizontal legs of the guides. During such pivoting the edges separate from each other.
In order to close the opening the edges fit snugly together and are often even provided with flexible or compressible seal strips that, in the closed position, are compressed between the panel edges to tightly seal the joint between adjacent panels. In addition it is standard to make the panels each of a pair of metallic or plastic skins forming the inner and outer faces, a pair of edge strips bridging the skins and holding them apart, and a mass of rigid closed-cell insulation filling the space between the skins and edge strips.
When used, for instance, as the door of a walk-in freezer or in a refrigerator plant, the doors are constituted to have a K-value of at least 0.5 and often as little as 0.2. In such an application the hinges are applied on the outside or warm side and the door rolls up onto this warm side. Thus when the door is rolled up, the edges separate on the cold side and the seals between adjacent panels, which are quite cold, are exposed to warmer air. The result is frost on the seals. The door is normally held open as little time as possible so that this frost does not have time to melt and can, with time, build up enough to interfere with operation of the door. Furthermore the frost can freeze the two panels together, so that the seals tear when the door is opened.
It is therefore an object of the present invention to provide an improved roll-up sectional door.
Another object is the provision of such an improved roll-up sectional door which overcomes the above-given disadvantages, that is which will not allow frost to build up on the panel edges.
A sectional roll-up door has according to the invention two generally planar panels having confronting longitudinally extending edges, a hinge between the panels at the edges, a seal extending longitudinally along one of the edges and operatively engageable with the other of the edges, and an element for heating the seal.
Thus according to the invention the seal is kept warm so that, when the door is opened and it is exposed to warm humid air, no frost will form on it. The amount of heating needed is modest and also serves to keep the seal flexible.
According to the invention each panel comprises a pair of parallel and spaced skins, edge strips bridging the skins and forming the edges, and a mass of insulation between the skins. The heater is provided at the edges. The seal can be an elastomeric tube and the heater a wire extending longitudinally inside the tube. Alternately the heater includes a hollow housing extending longitudinally along the edge and a heating element inside the housing. This housing can be fixed to the other edge to engage the seal of the one edge or it can be fixed to one of the skins and bridge the gap between the panel edges. In this latter case the hinges are on the other of the skins. The housing is aluminum.
The heater can also be an element extending longitudinally along the one edge. In this case the seal is an elastomeric strip and extends along an inside face of the edge strip forming the one edge. An insulating strip is provided between the heating element and the insulation mass in the panel.